"Overall this is very encouraging and reinforces the idea that the milk supply is safe," study leader William Flynn said.

Cows are given antibiotics and other drugs to keep them healthy, and some of them can end up in milk. While low levels of some drugs are permitted in milk, amounts above certain levels are illegal, the AP reported.

The FDA will use the study findings to try and reduce drug levels in milk even more, Flynn said.

The study was launched by the FDA in 2012 over concerns from public health groups about the levels of antibiotics in milk and other food products.

While the findings show that drug residues in milk are "a small problem," there should be expanded testing to reduce levels even more, David Plunkett, of the Center for Science in the Public Interest, told the AP.

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Last Ebola Patient in Liberia Discharged From Hospital

The last Ebola patient in the West African nation of Liberia was discharged from treatment on Thursday.

While there was a ceremony in the capital city of Monrovia to mark the event, officials warned that Liberia was still weeks away from being declared free of the deadly disease. They noted that there have been recent Ebola flare-ups in neighboring Sierra Leone and Guinea, the two other countries hardest hit by the large outbreak, The New York Times reported.

Liberian health officials are still tracking more than 100 people who may have been exposed to the Ebola virus. As of Thursday, no new cases of the disease had been confirmed in the country for the past 13 days.

"(The ceremony) was touching, it was pleasing, there was a lot of excitement because we feel that this is a victory," Tolbert Nyenswah, the deputy health minister in charge of Liberia's fight against Ebola, said in a telephone interview with The Times.

"But it's not over yet," he added. "We are still cautioning people. We told them they must still protect their villages, their towns. They should report any suspicion of Ebola to the health teams. We still have a response that is tight. Yeah, we made that point."

More than 9,800 people have died in the outbreak, including 4,117 in Liberia.